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NB6, NB6W, NB6Plus4, NB6Plus4W, NB6Plus4Wn User Guide YML854Rev1
138 www.netcomm.com.au
CHAPTER 6: GLOSSARY
ARP (Address Resolution Protocol )
ARP is a TCP/IP protocol for mapping an IP address to a physical machine address that is recognized in the
local network, such as an Ethernet address.
A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on
the network that has the IP address in the request then replies with its physical hardware address.
Inverse ARP (In-ARP), on the other hand, is used by a host to discover its IP address. In this case, the host
broadcasts its physical address and a RARP server replies with the host’s IP address.
DHCP (Dynamic Host Configuration Protocol)
When operates as a DHCP server, the ADSL Router assign IP addresses to the client PCs on the LAN. The
client PCs “leases” these Private IP addresses for a user-defined amount of time. After the lease time expires,
the private IP address is made available for assigning to other network devices.
The DHCP IP address can be a single, fixed public IP address, an ISP assigned public IP address, or a private
IP address.
If you enable DHCP server on a private IP address, a public IP address will have to be assigned to the NAT IP
address, and NAT has to be enabled so that the DHCP IP address can be translated into a public IP address.
By this, the client PCs are able to access the Internet.
LAN (Local Area Network) & WAN (Wide Area Network)
A LAN is a computer network limited to the immediate area, usually the same building or floor of a building. A
WAN, on the other hand, is an outside connection to another network or the Internet.
The Ethernet side of the ADSL Router is called the LAN port. It is a twisted-pair Ethernet 10Base-T interface. A
hub can be connected to the LAN port. More than one computers, such as server or printer, can be connected
through this hub to the ADSL Router and composes a LAN.
The DSL port of the ADSL Router composes the WAN interface, which supports PPP or RFC 1483 connecting
to another remote DSL device.
NAT (Network Address Translation) IP Address
NAT is an Internet standard that translates a private IP within one network to a public IP address, either
a static or dynamic one. NAT provides a type of firewall by hiding internal IP addresses. It also enables a
company to use more internal IP addresses.
If the IP addresses given by your ISP are not enough for each PC on the LAN and the ADSL Router, you
need to use NAT. With NAT, you make up a private IP network for the LAN and assign an IP address from
that network to each PC. One of some public addresses is configured and mapped to a private workstation
address when accesses are made through the gateway to a public network.
For example, the ADSL Router is assigned with the public IP address of 168.111.2.1. With NAT enabled,
it creates a Virtual LAN. Each PC on the Virtual LAN is assigned with a private IP address with default
value of 192.168.2.2 to 192.168.2.254. These PCs are not accessible by the outside world but they can
communicate with the outside world through the public IP 168.111.2.1.